1. Field of the Invention
The present invention relates generally to a pre-connectorized fiber optic distribution cable and, more particularly, to a pre-connectorized fiber optic distribution cable having an overmolded mid-span access location that compensates for span length measurement differences.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result, there is a need for connecting remote locations to a fiber optic distribution cable in order to provide broadband services to an end user, commonly referred to as a subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH) and “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” networks. To provide these services to the subscriber, FTTx networks must include a large number of interconnection points, also referred to herein as “tap points,” at which one or more optical fibers of a distribution cable are interconnected with optical fibers of one or more cables leading to a subscriber location. In addition, in order to reduce installation labor costs in FTTx networks, communications service providers are increasingly demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems.
To supply the large number of tap points needed and to satisfy the demand for plug-and-play systems, it is apparent that more efficient methods of providing mid-span access locations along the length of a distribution cable are needed. Presently, to perform a mid-span access of a distribution cable, a field technician first removes a section of the cable sheath at a convenient location along a previously installed distribution cable. Once the sheath is removed, the technician gains access to preselected optical fibers through the cable sheath, severs the accessed optical fibers and withdraws a useable length of the terminated optical fibers from the distribution cable. The useable length of the terminated optical fibers provides the field technician with sufficient length to splice one or more optical fibers of a cable comprising a lesser amount of optical fibers than the distribution cable (typically referred to as a “drop cable”) to the preselected optical fibers of the distribution cable. After splicing is completed, the mid-span access location is typically covered using an enclosure designed to protect the splices and the exposed section of the distribution cable. A benefit to this approach is that the distribution cable may be installed without consideration to the proximity of the mid-span access location to a convenient location in the network, such as a telephone pole, hand-hole or optical connection terminal. Since mid-span access is performed in the field following installation of the distribution cable, the field technician may position the mid-span access at any desired location in the network along the length of the distribution cable. The relatively difficult and time consuming process of creating the mid-span access, however, must be accomplished by a highly skilled technician at a significant cost and under less than ideal field working conditions.
Several approaches have been developed to overcome the disadvantages of accessing, terminating and splicing optical fibers in the field. In one approach, the splicing of drop cables to the distribution cable is performed at a factory during the manufacturing of the cable. The preterminated distribution cable, including the main cable, drop cables and associated splice closures, are assembled and wound onto a cable reel to be delivered to the service provider for installation in the network. Accordingly, favorable conditions in the factory for making high quality optical splices may be utilized, thereby increasing splice quality and also reducing the difficulty and expense, and the unfavorable conditions associated with splicing in the field. One disadvantage of this approach is that the drop cables and the relatively bulky and inflexible splice closures are attached to the distribution cable prior to installation. Accordingly, installation through small diameter conduits and over sheave wheels and pulleys is substantially more difficult, and sometimes impossible. Another disadvantage is the fact that if a mid-span access location is unused following installation, the expensive and obtrusive splice closure and drop cables remain attached to the distribution cable. More importantly, drop cables attached to the distribution cable in the factory during manufacture have a predetermined length. As a result, improper location of the mid-span access location due to differences between the pre-engineered span length measurement and the actual span length measurement following installation of the distribution cable can only be mitigated using the predetermined length of drop cable provided from the factory. Such differences, referred to herein as “span length measurement differences” typically result from network measurement miscalculations, installation errors, and differences between the proposed locations of telephone poles, hand holes, pedestals, etc. and their installed locations. If the mid-span access location on the installed distribution cable is located too far from the desired location, the drop cable may not have sufficient length. On the other hand, if the mid-span access location on the installed distribution cable is located too near the desired location, an excessive amount of drop cable slack must be managed. In contrast, a pre-connectorized fiber optic distribution cable having a predetermined mid-span access location that provides access to the connectorized optical fibers allows a field technician to readily interconnect a tether having a customized length to the distribution cable following installation to compensate for any span length measurement differences.
In another factory-manufactured approach, preselected optical fibers are accessed, severed and prepared “splice-ready” at the mid-span access location for splicing to optical fibers of one or more drop cables in the field following installation of the distribution cable. The mid-span access location in this approach is encapsulated with a protective structure (e.g., closure) for cable reeling, shipping, cable unreeling and installation that is removed and discarded to gain access to the splice-ready optical fibers following installation of the distribution cable. The optical fibers of the drop cables are then spliced to the splice-ready optical fibers at the mid-span access location and a protective splice closure is added around the mid-span access location to protect the optical splices and the exposed section of the distribution cable. There are several advantages to splicing the drop cables to the distribution cable in the field following installation of the distribution cable. First, the drop cables can be added only when needed in order to defer labor and material costs. Second, drop cables of customized length can be used to mitigate improper location of the mid-span access location due to span length measurement differences. However, there are disadvantages as well. While terminating and preparing splice-ready optical fibers in the factory significantly reduces the amount of labor required to connect subscribers to a mid-span access location, it is still necessary to splice the optical fibers of the distribution cable to the optical fibers of the drop cables in the field, oftentimes at an inconvenient location or under less than ideal working conditions. Another disadvantage is that a relatively expensive splice closure must be added to the distribution cable assembly at the mid-span access location in the field to protect the optical splices and the exposed section of the distribution cable, thereby increasing installation complexity as well as labor and material costs. In contrast, a pre-connectorized fiber optic distribution cable having a predetermined mid-span access location that provides access to the connectorized optical fibers allows a field technician to readily interconnect a tether having a customized length to the distribution cable following installation only when needed and without the addition of a relatively expensive splice closure.
Accordingly, it would be desirable to provide a factory-assembled fiber optic distribution cable for accessing one or more preterminated and pre-connectorized optical fibers at a mid-span access location having an outer diameter that is only minimally larger than the outer diameter of the distribution cable. It would also be desirable to provide a pre-connectorized fiber optic distribution cable having one or more low profile mid-span access locations that is suitable for both buried installations (e.g., through small-diameter conduit) and aerial installations (e.g., over sheave wheels and pulleys). It would also be desirable to provide a pre-connectorized fiber optic distribution cable that allows a field technician to readily interconnect a tether having a customized length to the distribution cable following installation to mitigate improper location of the mid-span access location due to span length measurement differences. It would further be desirable to provide a pre-connectorized fiber optic distribution cable that allows a field technician to readily interconnect a tether having a customized length to the distribution cable following installation only as the mid-span access location is needed to provide service to subscribers without the addition of a relatively expensive splice closure.